Carnivora Lecture Review

Carnivora Evolution and Ecology

Overview

• This session outlines the evolutionary history of carnivora, explores their morphological and functional characteristics, examines their life history features, and reviews a case study.

Emergence of the Carnivora

• The order Carnivora belongs to the grandorder of placental mammals (Ferungulata), which includes true ungulates and pangolins.
• Pangolins are more closely related to Carnivora within the mirorder Ferae.
• Carnivoramorpha, the clade containing "carnivoran-like" forms, emerged in the Paleocene of North America around 60 million years ago.
• The crown group, Carnivora (all living carnivorans), appeared around 42 million years ago in the Middle Eocene.
• Molecular phylogeny suggests Carnivora is a monophyletic group.

Taxonomic Classification

• Domain: Eukaryota
• Kingdom: Animalia
• Phylum: Chordata
• Class: Mammalia
• Grand Order: Ferungulata
• Mirorder: Ferae
• Clade: Carnivoramorpha
• Order: Carnivora

Key Adaptation

• Carnassial tooth: first appeared ~50 million years ago, common to Carnivoramorpha.

Ecological Context

• Early carnivorans were small.
• Creodonts (extinct orders within Ferae) and mesonychians (carnivorous ungulates in Ferungulata) dominated apex predator niches during the Eocene.
• Climactic warming in the earliest Eocene may have driven evolutionary changes.
• By the Oligocene, carnivorans became a dominant group of apex predators.
• In the Miocene, most extant carnivoran families diversified and became primary terrestrial predators in the Northern Hemisphere.

Divergence within Carnivora

• Two suborders diverged approximately 58-59 million years ago:
  • Caniformia (dog-like)
  • Feliformia (cat-like)
• Divergence is based on the bony structures surrounding the middle ear (auditory bullae).

Key Differences Between Feliforms and Caniforms

Feliformia Families

• Nandiniidae (African palm civet)
• Felidae (cats: small cats, tigers, leopards, jaguars, lions, cheetahs, ocelots, etc.)
• Prionodontidae (Asiatic linsangs)
• Viverridae (Civets, genets & oyans)
• Hyaenidae (Hyenas)
• Herpestidae (Mongooses)
• Eupleridae (Malagasy mongooses & civets)

Caniformia Families

• Canidae (dogs):
  • Canina (wolf-like canids)
  • Cerdocyonina (South American canids)
  • Vulpini (fox-like canids)
  • Urocyon genus (gray & island fox)
• Ursidae (Bears):
  • Ailuropodinae (Pandas)
  • Tremarctinae (Short-faced bears)
  • Ursinae (all other bears)
• Pinnipeds:
  • Odobenidae (Walruses)
  • Otariidae (Eared seals / Sea lions)
  • Phocidae (Earless seals / True seals)
• Musteloids:
  • Mephitidae (Skunks & Stink badgers)
  • Ailuridae (Red Panda)
  • Procyonidae (Raccoons, olingos, ringtails, coatis, cacomistles, kinkajous)
  • Mustelidae (Weasels, otters, wolverines, polecats, badgers, martens, grisons)

Apex Predators

• Apex Predator: Species occupying the top trophic position in a community; often large-bodied and specialized hunters.
• Mesopredator: Occupies a trophic position below apex predators; context dependent.

Mammalian Carnivore Size and Energetics

• Two broad dietary groups based on size:
  • Smaller carnivores (<20 kg): Eat very small prey (invertebrates and small vertebrates).
  • Larger carnivores (>20 kg): Specialize on large vertebrates.
• Energetic constraints of diet lead to a 21.5 kg transition.

Optimal Foraging Theory

• Organisms maximize their net energy intake over time.
• Key variables:
  • $E$ – Energy in food item
  • $h$ – Handling time (capture, killing, eating, digesting)
  • $s$ – Search time

Maximizing Net Energy Gain

• Pursuing and subduing large prey requires more energy.
• Larger organisms use and consume more energy but do so relatively less per unit of body mass than smaller organisms.
• Larger carnivores achieve a higher net gain rate by concentrating on large prey.
• Carnivores at the upper limits of each group (

Maximum Size

• Predicts a maximum carnivore mass of approximately a ton.
• Consistent with the size of the largest extinct species.
• Extremely large carnivores would have been heavily reliant on abundant large prey, explaining why they are rare and vulnerable to extinction.

Interference from Human Super Predators

• Humans impact species assemblage, environmental productivity, landscape predation risk, large herbivores, large carnivores, mesopredators, and ecosystem services.

Size and Life History Traits

• An upper limit body mass of 34 kg (corresponding with an average mass of 13–16 kg) marks a transition between extrinsically- & self- regulated carnivores.
• Small carnivores:
  • Fast reproductive rates
  • Fast development
  • Higher densities
• Large carnivores:
  • Slow reproductive rates & development
  • Extended parental care
  • Sparsely populated territories
  • Propensity towards infanticide, reproductive suppression, alloparental care & cooperative hunting.
• Self-regulation in large carnivores may ensure resources are not overexploited.
• The expression of traits that contribute to self-regulation (e.g., reproductive suppression) depends on social stability.
• Predator–prey dynamics hard to study in the absence of predator persecution.

Sociality

• Groups form when benefits exceed costs.
• Benefits:
  • Security (decreased chance of being preyed upon)
  • Information sharing
  • Thermoregulation
  • Competitive advantage (conspecifics / competing species)
  • Cooperative food acquisition
  • Cooperative rearing of young
• Costs:
  • Parasitic infection
  • Disease transmission
• Sharing a carcass with genetic relatives better than losing it to scavengers helps explain group hunting & optimal pack size.

Case Study: Gray Wolves

• Prey size ranges from 1 - 1000 kg.
• Diet depends on availability and experience.
• Opportunistic generalist predator but often specializes on large ungulates.
• Prey is nutritionally interchangeable.
• Co-evolved with prey species in an evolutionary “arms race”.
• Geographically diverse and highly adaptable.
• Found in a variety of habitats.

Wolf Taxonomy

• Phylogenetic tree of wolf-like canids.
  • Caninae 3.5 Ma
  • Domestic dog
  • Gray wolf
  • Coyote
  • African wolf
  • Dhole
  • Golden jackal
  • Ethiopian wolf
  • African wild dog
  • Side-striped jackal
  • Black-backed jackal

Wolf Physiology

• Marathon runners of the animal kingdom.
• Endurance:
  • Efficient respiratory system
  • Slender frame, long legs & narrow chest provide efficient running.
  • Slow twitch & fast twitch muscle fibres
  • Large paws for traversing snow
• Thermoregulation:
  • Double layer fur coat
  • Lots blood vessels in paws help prevent overheating

Wolf Skull and Dentition

• Reflects predatory habits.
• Larger closing muscle (temporalis) than found in herbivores.
• Connected to prevent dislocation while undergoing severe stress while clinging to prey.
• Long skull allowing maximal opening.
• Bone reinforced with diagonal lines crossing the skull to resist fractures.
• Not as extremely specialised as other carnivores.
• Examples:
  • Felid skulls have large closing muscles or solidity.
  • Hyenas have strong jaws, premolars & muscles for bone crushing.
  • Mustelids lack locking hinge adaptation for locking around prey much larger than itself (Canis lupus).

Dentition Details

• 42 teeth
• Canines:
  • Puncture & grapple the prey, assisted by the incisors.
  • Elliptical cross section; longer than they are wide enabling them to resist front to back stresses.
• Incisors:
  • Positioned in front of the canines; permits separate functioning.
  • Nipping & pulling at live prey, removing tissue, handling non-struggling food (e.g. berries), Ectoparasite removal.
• Premolars:
  • Multi-purpose teeth used for tearing & chewing.
• Carnassial teeth:
  • Primarily utilised in the consumption of food
  • Self-sharpening; upper & lower blades shear past each other trapping & cutting meat or hide when the jaw closes.
• Molars:
  • Surface adapted to crushing & grinding.
  • Not as reinforced or specially shaped for bone crushing as in other carnivores e.g. hyena.

Wolf Digestion

• Short guts; carnivorous diet is highly digestible.
• Quick maximal intake; little mechanical breakdown of food in the mouth (up to 10kg in a sitting).
• Roughage: Mixes food with indigestible components (e.g. hair).
• Permits rapid emptying of the gut & further feeding; minimises loss to scavengers.
• Organs & muscle consumed first.
• Inefficient early digestion; protein quantity likely restricts enzyme function.
• Hide & bones consumed last, not entirely digestible.
• Degree consumed is a good indicator of food availability.
• Hair is wrapped around bone fragments before the wolf passes faecal matter to prevent damage.
• Pack size influences carcass utilization.

Food Availability & Storage

• Stores surplus food energy as fat (generally ~ 15% of overall weight).
• Often food limited, typically existing at lower end of fat content, often with depleted bone marrow fat stores (a precursor to starvation).
• Can survive for long periods with low food consumption.
• Weight is lost daily.
• Ability to alter enzyme systems according to diet & can recover from weight lost during fasting.
• Adapted for feast - famine diet.
• Still know relatively little of the bodily functions that deal with the starvation process.
• Wolves also cache surplus food.

Wolf Senses

• Used to locate, track & assess prey but also very important in social interactions.
• Smell is key: The surface area of wolf noses receptive to smell is 14 times that of our own & up to 100 times more sensitive.
• Sight: Equal to our own, but their night vision is far more developed.
• Retain a scotopic (low-light) eye design consistent with nocturnal origins.
• Hearing: Allows determination of noises as far as 6 miles away in forested areas & 10 miles in open tundra.

Wolf Communication

• Auditory:
  • Howling: Announce territory, locate pack members, social bonding exercise.
  • Wide range of vocalisations: Yips, Grunts, Snarls, Whimpers
• Olfactory:
  • Scent is socially important.
  • Individual recognition via pre-caudal scent gland at the base of the tail.
  • Unique odour in body & excretions.
  • Scent marking: Territorial boundaries; Valued resources (e.g. carcasses, den sites); Urination & defecation; Glands in paws which they will often scratch on the ground after scent marking.
• Visual:
  • Complex body language.
  • Positioning of the tail, ears, eyes & facial expression are all used to convey a range of emotional states & intentions.

Domestication and New Niches

Digestion of Starch in Dogs

• Novel adaptations allow early ancestors of modern dogs to thrive on a diet rich in starch, relative to the carnivorous diet of wolves.
• Change in ecological niche; likely selection pressure.
• Several groups of genes in humans & dogs have been evolving in parallel for thousands of years, including those related to diet, digestion, neurological processes, & disease

Resource Acquisition

• Finding resources:
  • Let / encourage them to come to you
  • Navigation, timing.
• Skill:
  • Sourcing & capture
  • Handling & processing
  • Optimal foraging
• Strategy:
  • Forage
  • Scavenge (or steal)
  • Beg
  • Hunt
  • Team-up

Lecture Summary

• The Carnivora evolved ~ 42 million years ago (Middle Eocene).
• Carnassial type cutting tooth was a key characteristic adaptation.
• ~ 20 MYA (Miocene): Most of the extant carnivoran families diversified and became the primary terrestrial predators in the Northern Hemisphere.
• Species physiology & behaviour is suited to their niche & hunting style.
• Size is affected by optimal foraging & energetic restrictions.
• Apex & mesopredators have different life histories & attributes.
• Species evolving in parallel may share similar attributes / adaptations.